182 



WEED FLORA OF IOWA 



Rattle-box (Crotalaria sagittalis L.). 



Description. — A hairy annual from 3 in-1 ft. high, with a small 

 tap root; stem branched, villous, terete or wing-margined; leaves 

 oval or oblong-lanceolate, from %-% i n - wide, edge of the leaf en- 

 tire or somewhat wavy and hairy; stipules united and decurrent 

 on the stem, becoming inversely arrow-shaped; peduncles produce 

 a few yellow flowers about 14 in. in diameter; calyx 5-cleft, stand- 

 ard of the flower large, heart-shaped ; keel scythe-shaped ; stamens 

 monadelphous, anthers of two sizes, 5 smaller and roundish; pod 

 large, inflated, bears a close resemblance to that of the garden pea, 

 greenish at first, becoming blackish varying in size from %-l in. 

 in length and about 1 in. in diameter; seeds from 1/2-1/10 in. in 

 diameter, flattish, kidney-shaped, when mature breaking away from 

 the point of attachment and rattling in the pod, hence the name 

 "rattle-box". 



Fig. 103. Rattle-box (Crotalaria sagittalis). Common in sandy soil, Missouri 



river bottoms. 

 (Photographed by Colburn.) 



